This invention relates to a transport system in which a first network is coupled to a second network including transport apparatus.
In recent years, users' demands for a guaranteed bandwidth service in which the quality of communication is guaranteed are increasing. The guaranteed bandwidth service is a communication service that guarantees a bandwidth set out in an agreement with the user.
Internet Protocol/Multi-Protocol Label Switching (IP/MPLS) networks are wide-spread as a backbone network for providing the guaranteed bandwidth service to users. A packet is transferred in an IP/MPLS network with the use of label switching, instead of the traditional IP routing. An end-to-end logical path (communication path) is built by distributed control from communication apparatus used to construct an IP/MPLS network so that a bandwidth is guaranteed for each section.
Telecommunication carriers that use a transport network to provide the guaranteed bandwidth service are increasing in number. Centralized control-type communication protocols, such as Multi-Protocol Label Switching-Transport Profile (MPLS-TP), are used as a communication protocol for building a transport network. Transport networks can provide a logical path that is superior in confidentiality to one in traditional IP/MPLS networks. Transport networks are also rich in Operation, Administration, and Maintenance (OAM) functions for monitoring a communication route for a failure and QoS functions for guaranteeing the quality of service.
These advantages of transport networks are taken into consideration in standardization by the Internet Engineering Task Force (IETF) and others, where an IP interworking technology is beginning to be explored, which attempts to sophisticate IP services by using a traditional IP/MPLS network as a network that is coupled to users' bases for the purpose of keeping the cost low, using a transport network as a core network, and coupling these networks to each other.
In order to accomplish this IP interworking, the transport network and the IP/MPLS network need to be coupled to each other by one of centralized control, which is a network control method used in transport networks, and distributed control, which is a network control method used in IP/MPLS networks. Centralized control is inferior to distributed control in that the load concentrates on the management server and in terms of flexibility in network designing, but allows one to grasp the overall state of the network, which gives centralized control superiority in optimum route setting and the ease of management such as switching routes in the event of a failure. Distributed control, on the other hand, is superior to centralized control in terms of flexibility in network designing and scalability because the respective apparatus operate in an autonomous manner, but does not allow each apparatus to grasp the overall state of the network, which makes it difficult to optimize route settings and to clarify the location of a failure and the impact of the failure. It is therefore concluded that, with the sophistication of IP services as the aim, IP interworking is accomplished desirably by centralized control.
The discussion next focuses on the logical path building method in transport networks and the logical path building method in IP/MPLS networks. A logical path in a transport network is built generally by an administrator by statically setting a route of the logical path and a guaranteed bandwidth. A logical path in an IP/MPLS network is built by node apparatus by dynamically setting a route based on parameters (the link cost, hop count, and the like) of the network. When the guaranteed bandwidth service is provided, a logical path in an IP/MPLS network is built by using a dynamic bandwidth reservation protocol such as Resource Reservation Protocol-Traffic Engineering (RSVP-TE).
In IP interworking, a method of causing the entire transport network to seem like one virtual router is known in which a virtual router control server gathers control information exchanged over the IP/MPLS network and executes processing that corresponds to the control information (see JP 2013-26829 A, for example).